for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture April 13, 2012Coordinator Weekly IPM report: Stanton Gill, Extension Specialist, IPM for Nursery, Greenhouse and Managed Landscapes, sgill@umd.edu. 301-596-9413 (office) or 410-868-9400 (cell)

Regular Contributors: Pest and Beneficial Insect Information: Stanton Gill and Paula Shrewsbury (Extension Specialists) and Brian Clark (Extension Educator, Prince George’s County)Disease Information: Karen Rane (Plant Pathologist) and David Clement (Extension Specialist)Weed of the Week: Chuck Schuster (Extension Educator, Montgomery County)Cultural Information: Ginny Rosenkranz (Extension Educator, Wicomico/Worcester/Somerset Counties)Fertility Management: Andrew Ristvey (Regional Specialist, Wye Research & Education Center)Design, Layout and Editing: Suzanne Klick (Technician, CMREC)

In This Issue...

If you work for a commercial horticultural business in the area, you can report insect, disease, weed or cultural

plant problems found in the landscape or nursery to

sklick@umd.edu

TPM/IPM Weekly Report

- Dry and sunny weather- Anthracnose- Cold damage- Tuliptree scale- Fireblight- Brown marmorated stink bug- Four-lined plant bug- Iris leafspot- Boxwood leafminer- Brand canker on rose- Disease update (from Rich Anacker)- Lilac borer- Emerald ash borer: cost calculator- Assassin bugs- Willow leaf beetle

Beneficial of the WeekWeed of the WeekPlant of the WeekPhenologyDegree DaysContacts for ExpertsConferences

Integrated Pest Management for

Commercial Horticulture

www.ipmnet.umd.edu

Sunny – But Awfully DryThe sunny, dry weather continues to create conditions for very strong sales at garden centers. The trouble now is that it is getting too dry which will impact the success of transplanted trees, shrubs and flowers unless customers are keeping the plants watered. Think back to the spring of 2011 when we had record rainfall, followed by record high temperatures and drought during the summer. We do not want a repeat of last season’s weather, but a little rain would be helpful. Expect to start seeing the impact showing up with dieback of newly transplanted plants that are not getting enough water.

The whole East Coast is experiencing this dry spell. I (Stanton) was in Delaware this week and could see how much the soil is cracking. Be sure to irrigate new transplants well this year to avoid problems in the future.

Rich Anacker, A&A Tree Experts noted that “One thing I haven’t noticed this spring are Gator Bags. Trees planted last fall could really use them this spring since it has been so dry. If you do use them, make sure to top them off on a regular basis. I visit numerous properties that have them, but when I pick them up, they are empty!”

We need your input. Please call me (Stanton) at 410-868-9400 or send an email to sgill@umd.edu if you see insects or diseases active in your area. This information will make these reports more useful if we

have everyone’s input from all parts of the state.

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Frost DamageWe continue to receive reports of frost damage. Marty Adams is finding damage on the new growth of Clethra barbinervis, Stachyrus praecox, Corylopsis spicata and Disanthus cercidifolius. Rich Anacker is reporting a lot of damage this spring on various plants especially on hydrangea, Magnolia stellata, camellia, spirea, and boxwood. Kevin Nickle, ProLawn Plus, Inc., brought in a boxwood sample with both leafminer damage and frost damage.

Colletrotrichum on Osmanthus americanusPhotos: Marty Adams, Bartlett Tree Experts

Anthracnose (Colletotrichum) DiseaseMarty Adams, Bartlett Tree Experts, is reporting that their lab confirmed Colletotrichum spp. in samples of Prunus laurocerasus in Ellicott City and Osmanthus americanus in Silver Run. In both cases, there was premature defoliation of older foliage due to heavy leaf spotting and noticeable yellowing of infected leaves. Raking up infected leaves helps reduce the spread of this disease. Depending on the severity of the infection, fungicides may be necessary.

Tuliptree scale on magnolia

Tuliptree ScaleSecond instar tuliptree scale were found on magnolia on the Eastern Shore this week. These 2nd instars look like black freckles along the stem. The scale will swell up through the spring and summer and mature late summer with crawlers produced in this area in September. Control: Apply a foliar spray of 1% oil or a soil drench of phosmet (Imidan) or dinotefuran (Safari, Transtect) at this time.

Boxwood leafminer and cold damage on boxwood

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Four-lined plant bug nymph and damage on Deutzia gracilis leaf

FireblightPaul Wolfe, Integrated Tree Care, said he is seeing wilting tip growth on callery pears in the Montgomery County area this week. He said in the past this has been the start of fireblight on these trees. If someone sees pears with dieback please submit a sample to Karen Rane at the plant diagnostic lab in College Park.

Brown Marmorated Stink BugWe are finding adult stink bugs outdoors on ornamental woody plants and on apple trees in Carroll, Howard and Montgomery counties this week. There is no indication of feeding yet, but they are out. Three were caught this weekend in a black light trap in Westminster, MD.

Iris Leaf SpotCarol Allen, UMD research graduate assistant, sent in a photo of iris leaf spot caused by the fungus, Didymellina macrosppora. For more information on this disease, go to the Virginia Tech web page at: http://pubs.ext.vt.edu/450/450-600/450-600.html

Four-lined Plant BugsMarie Rojas is reporting that four-lined plant bugs are out and feeding on a variety of herbaceous plants including penstemon and mint in Bethesda. This bug feeds on over 250 species of herbaceous and woody plants. There is only one generation of this insect per year. Damage occurs early and plants grow out of it through the season.Monitoring: Look for white to dark colored spots on the foliage with plant damage concentrated on the upper foliage of the plant. The four-lined plant bug is a sucking insect that injects a toxin that discolors the foliage.Control: If necessary, this pest is easily controlled by insecticidal soap or neem products. Acephate (Orthene) is also effective.

Iris leaf spotPhoto: Carol Allen

Boxwood Leafminers Marie Rojas is finding that boxwood leafminers are still in the pupal stage in Beallsville. Here at the research center in Ellicott City, there has been no adult emergence yet.

Brand Canker Of RoseNorm Brady, Bartlett Tree Experts, reported that Lorraine Graney, Bartlett Lab, identified brand canker of rose (Coniothyrium wernsdorffiae) in Knock OutTM roses from Princess Anne. Look for small, dark reddish spots on the canes which often start around wounds. These spots enlarge and darken, becoming covered with tiny fruit-ing structures (look like black dots). Cankers girdle and can kill the cane.Management: Avoid planting stock with cankers. Remove infected canes before budbreak. Be sure to sterilize pruners between cuts. Avoid injuries to the plants as much as possible and provide adequate winter protection.

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Assassin bug nymph

Disease Information From Rich Anacker, A&A Tree ExpertsRich Anacker, plant pathologist, is reporting that over the last several weeks he has visited numerous properties with plants exhibiting symptoms of Phytophthora root rot. Rich noted that most of his visual diagnosis is based on experience and has not been confirmed with any lab test. Rich pointed out that at the end of last summer we had a record amount of rain which he feels contributed to the extensive dieback of landscape plants seen this spring. Most of the landscape plants he has observed exhibiting symptoms of Phytophthora root rot are those known to be highly susceptible including arborvitae, blue hollies, boxwood, cherry laurel, European beech, Japanese holly, yew, and numerous others.

Since it is impossible to determine where the disease originated on newer plantings (from soil existing on site or brought in on plants), care should be taken during the plant replacement process. Based on Rich’s experience, he makes the following recommendations. If replacing a tree/shrub of the same species, as in a hedge row, remove infected plants and as much soil as possible without disturbing adjacent plants. If possible, improve drainage in planting area. Soil drench site to be replanted and all adjacent plants prior to planting with a product such as Subdue Maxx/Mefenoxam. Replace with clean soil and replant. Do not overfertilize any tree or shrub suspected to be infected with Phytophthora because they will die if they are infected. Mycorrhizae soil treatments are beneficial as long as they do not contain any fertilizer. If you do use mycorrhizae to help offset Phytophthora damaged trees/shrubs, clean equipment with disinfectant containing 10% bleach prior to treating any other trees/shrubs. Repeat soil treatments during high disease pressure years.

Lilac BorerWe put out pheromone traps for clear wing moth borers last week. No flight activity for lilac borer as of yet.

Emerald Ash Borer: Cost CalculatorCliff Sadof, Purdue University, announced this week that there is a new EAB cost calculator available on-line at http://extension.entm.purdue.edu/treecomputer/v2beta/. He noted that it is “driven by an invasion wave model where we estimate costs under the assumption that management would be most aggressive during the initial invasion. After most untreated trees are killed the population pressure and the management needs would be far lower.”

Beneficial Insect ActivityMarie Rojas, IPM Scout, is reporting hatch of assassin bugs in Beallsville this week. Look for these bright red/orange and black nymphs which hang around the cluster of eggs for a little bit after hatching. Assassin bugs are generalist predators that feed on insects including scale and Japanese beetles.

Willow Leaf BeetlePaul Wolf, Integrated Plant Care, reported that willow leaf beetle adults are active this week in Bethesda. Adult feeding by this beetle causes small round holes in the foliage of willow. When the larvae hatch, they skeletonize the foliage.Control: It depends – if the willow is in a highly visible location in the landscape, you may choose to treat the trees. If it is in a natural setting and your customer can live with skeletonized leaves then the tree will not die from the damage but they may be unattractive.

Willow leaf beetle larvae feeding damage

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Eggs of a tachinid fly parasitoid on the body of a squash bug Photo: http://agdev.anr.udel.edu)

Weed of the Week, Chuck SchusterPurple deadnettle, Lamium purpureum,(Photo B) is a common fall germinating, winter annual in the mint family. Often mistaken for henbit (photo A), this weed is found in turfgrass and landscape settings throughout the United States. Purple deadnettle has square hollow stems, no basal leaves, and the leaves are on a short petiole (photo C) which distinguishes it from henbit whose upper leaves are sessile or attached to the stem itself. Petiole length of the lower leaves will be longer than that of the upper leaves. The leaves of purple deadnettle are opposite, slightly pubescent (occurring with hairs) circular in shape with a toothed margin but are less deeply lobed than henbit.

C) Purple dead-nettle leaves on short petioles

B) Purple deadnettleA) Henbit

Photos: Chuck Schuster

Beneficial of the Week, Paula ShrewsburyFringe-legged Tachinid Fly – a parasitoid of stink bugs

With the invasion of the brown marmorated stink bug (BMSB) into the U.S., especially the mid-Atlantic region, there is an emphasis on identifying potential natural enemies of stink bugs. Just last week in our BMSB colony (yes - we are actually trying to raise BMSB) we found a tachinid fly, Trichopoda pennipes, which just happens to be a parasitoid that attacks members of the stink bug and other true bug families. This fly is native to North and South America. This parasitoid is about the size of a large housefly, has a black head with large brown eyes, a mostly black thorax, a bright orange abdomen, and transparent smoky wings. Most notable are the hind legs that bear a comb-like fringe of short hairs.

This tachinid fly begins its activity in late spring and feeds on nectar from flowers such as Queen Anne’s lace and meadowsweet. The adult fly may be seen hovering over other plants in search of prey on which to lay its eggs, most commonly squash bugs and southern green stinkbugs (and we hope BMSB). The female fly lays several small, pale-colored, oval eggs on the outer exoskeleton of a late instar nymph or an adult bug. When the eggs hatch, the larvae burrow into the bug. If several larvae are in one host, only one will survive. After feeding on the bug’s insides, the fly larva (maggot) emerges and falls to the ground where it pupates. Most importantly the bug dies during this process. After a few weeks, an adult fly emerges from the pupa and starts the cycle all over again. A female fly will oviposit on numerous bugs, laying up to several hundred eggs in her lifetime. There are up to three generations of the fly each year suggesting this tachinid parasitoid has the potential to significantly impact populations of true bugs. To date, surveys of BMSB have found adults with tachinid eggs on their bodies. Unfortunately, none of the tachinids have completed their development in BMSB. Further studies will be conducted on this parasitoid, along with others, to determine its potential as a biological control agent of BMSB.

Adult fringe-legged fly feeds on nectar prior to laying eggs on stink bugs and other true bug species Photo: Valter Jacinto, http://eol.org)

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Plant of the Week, Ginny RosenkranzVerbena canadensis ‘Homestead Purple’ is an herbaceous perennial that hugs the ground and bursts into bloom in mid spring and will continue to bloom with a dome of bright purple flowers until the cold and frost of fall. The flowers will attract butterflies and many other pollinators to their trumpet-shaped florets. Dead heading the 3 inch flower clusters will help the plant continue to bloom, but it is not a necessity. This warm winter has ‘Homestead Purple’ verbena blooming the first week of April on the Eastern Shore of Maryland, covering the ground with their fragrant deep purple flower clusters. Once established it is very heat and drought tolerant. Cold hardy from USDA zone 7A to 10, the plants will grow in many soil types, thriving in loamy or sandy, well drained soils with a neutral pH. Heavy soils or soils that stay wet during the winter may lead to the decline or death of the plants. The deep green foliage is coarsely scalloped and about 3-4 inches long and the plant will spread to about 3 feet round. Like many fast growing perennials, good ground preparation and a light application of fertilizer will keep the plants growing and blooming their best. Damping off can affect the plants grown in soils that hold too much water. Whiteflies and spider mites can attack the plants in very hot dry weather, but the fast growth of the plants and the abundant flowers will often hide the damage.

Verbena ‘Homestead Purple’Photos: Ginny Rosenkranz

Uppermost leaves can be triangular in shape. Leaf color is dark green, with the upper leaves becoming purple or red. The stems are square in shape and can grow up to sixteen inches in height branching from the base of the plant. Whirls of three to six, purple flowers occur in the upper leaves. The root system is fine and fibrous. The plant produces a small berry about two mm in diameter. Purple deadnettle spreads by seed.

The name deadnettle comes from the fact that it will not sting you as opposed to stinging nettle, Urtica, which will. The two plants are not closely related but they are similar. Urtica is that formic-acid wielding plant that zaps you with little stingers. Purple deadnettle can be eaten.

Control of purple deadnettle can be accomplished using post emergent products that include Imazaquin (Image), Metribuzin (Sencor) turf only, and 2,4 D + MCPP. A fall application of Dichlobenil (Barrier) (pre emergent) can help prevent this weed from being an issue in the spring.

Square stem of purple deadnettle

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PLANT PLANT STAGE (Bud with color, First bloom, Full bloom, First leaf)

LOCATION

Liriodendron tulipifera First leaf (April 11) Ellicott CityStewartia pseudocamellia First leaf (April 13) Ellicott City

Plant Phenology: What’s in bloom

Degree Days (As of April 12)Baltimore, MD (BWI) 247 Dulles Airport 251 Frostburg, MD 137 Martinsburg, WV 227 National Arboretum 321 Reagan National 357 Salisbury 419

Who can you contact for help with plant problems?Diseases:Karen Rane: rane@umd.edu, 301-405-1611 Go to www.plantclinic.umd.edu for information on how and where to submit suspected disease samples to her lab.

Insects:Stanton Gill: sgill@umd.edu, 410-868-9400 (cell) or 301-596-9413 (office) Paula Shrewsbury: pshrewsb@umd.edu, 301-405-7664Brian Clark: bpclark@umd.edu, 301-868-8780 (Brian covers Prince George’s County)

Weeds:Chuck Schuster: cfs@umd.edu, 301-590-2807

Soil Substrates Plant Fertility:Andrew Ristvey: aristvey@umd.edu, 410-827-8056

Horticulture:Ginny Rosenkranz: rosnkrnz@umd.edu, 410-749-6141 ext 106 (Wicomico, Worcester and Somerset counties)

Phenology Report For Silver Run, Maryland From Marty Adams, Bartlett Tree Experts

First Bloom:Trillium grandiflorum, Phlox stolonifera 'Sherwood Purple', Menziesia ciliicalyx (now reclassified as Rhododendron benhallii), Neviusia alabamensis, Fothergilla gardenii 'Mt Airy', Amalanchier nantucketensisAmalanchier fernaldii, Osmanthus americanus, and Sedum ternatum Full Bloom:Pieris floribunda, Halesia caroliniana, Croton alabamensis, Comptonia peregrina, Mukdenia rossii, Asimina triloba, Clematis 'Lagoon', Epimedium x niveum, Sorbus reducta, Enkianthus perulatus 'JL Pennock', Staphlea colchica, and Xanthoriza simplissisima

Stanton GillExtension Specialist

sgill@umd.edu

Paula Shrewsbury Extension Specialistpshrewsb@umd.edu

Ginny RosenkranzExtension Educatorrosenkrnz@umd.edu

Chuck SchusterExtension Educator

cfs@umd.edu

Karen Rane Plant Pathologistrane@umd.edu

Brian Clark Extension Educator bpclark@umd.edu

Andrew RistveyExtension Specialistaristvey@umd.edu

David ClementPlant Pathologist

hgic.umd.edu

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied.

CONTRIBUTORS:

University of Maryland Extension programs are open to all citizens without regard to race, color, gender, disability, religion, age, sexual orientation, marital or parental status, or national origin.

Thank you to the Maryland Arborist Association, the Landscape Contractors Association of MD, D.C. and VA, the Maryland Nursery and Landscape Association, Professional Grounds Management Society, and FALCAN for your

financial support in making these weekly reports possible.

Photos are by Suzanne Klick or Stanton Gill unless stated otherwise.

Upcoming Programs

MAA Pest WalkMay 17, 2012Location: Brookside Gardens, Wheaton, MD

Invasive Species Identification and Management SeminarMay 23, 2012 9:30 -3:15Location: 12055 Government Center Parkway, Fairfax, VACost: Free, but registration is required. To register please go to: http://ffxpest.eventbrite.comContact: Jack Baggett 703-324-5542, John.baggett@fairfaxcounty.gov

ASCFG Mid-Atlantic Regional MeetingJune 18, 2012Roost Flowers and DesignLocation: Virginia Beach, Virginiaascfg.org

MNLA Field DayJune 21, 2012Location: D.R. Snell Nursery, Union Bridge, MD

Maryland Christmas Tree Association’s Summer MeetingJune 30, 2012 (Saturday)Location: Taylor Sines Woodlake Tree Farm, Oakland, MDContact: 410-452-9793

2012 Perennial Plant SymposiumJuly 4 - 10, 2012Location: Boston, Massachusettsperennialplant.org

OFA Short CourseJuly 14 - 17, 2012Location: Columbus, Ohioofa.org

OFA Perennial Production ConferenceSeptember 10 - 12, 2012Location: Grand Rapids, Michiganofa.org